EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: BreakingOhmsLaw on May 15, 2020, 11:09:47 am
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Hi everybody,
Everybody who hand-solders SMD parts by hand knows the annoying problem that parts keep sticking to your tweezers. Either because of flux residue or because they have magnetized.
Cleaning off the flux works well enough with PCB cleaner, but how do you demagnetize your tweezers?
I am thinking about designing a small degausser for hand tools, do any of you have a proven solution? You can get demagnetizers for watchmakers for around €20 on Fleabay and Ali, but do they work? They also have a button to activate, but a one-handed solution would be preferred for obvious reasons. My guess is that they don't contain more than a transformer and a coil, and rely on distance to gradually decreasing the magnetic field. I'm thinking more along the lines of degaussing circuits that old CRT monitors used to have. Simple ones just had a PTC, better ones threw more circuitry at it.
Cheers
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I put them in the same isopropyl alcohol bath when I'm cleaning PCBs. After that I wipe off any remaining crud, they come out nice and clean.
As for magnetization problems, I buy non-magnetic ones. :D
I do have one of those demagnetizers, and yes they are just an inductor and a push button. It does work well with my other tools. You can get them for as low as ~8€.
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Isn't Stainless Steel non magnetic ??
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I find that most "non-magnetic" tweezers don't hold that promise entirely. Your milage may vary.
I have a pair of ceramic tweezers, bu they have their own issues, mainly being much thicker than a steel tool.
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I agree, a number of the "non-magnetic" and "anti-magnetic" tweezers I have gotten in the past where some type of steel that was not currently magnetized, and would regularly become slightly magnetic after enough heating and cooling cycles around soldering temperatures. enough to move around a staple.
to this end I just have a tiny 1.8V 500mA transformer that I have mostly shorted in to a coil of wire, insert the part, press the button a few times and the part comes out demagnetized without really ever risking overheating the transformer. (500mA * 70 turns of not very thick enamel wire from memory)
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It's like "waving a red rag at a bull" hahaha....
But how do you like "Breaking Ohms Law" ?? ;D
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Isn't Stainless Steel non magnetic ??
It depends on the type of stainless steel. They vary from pretty much totally non-magnetic to somewhat magnetic.
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Ceramic tweezers.
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IPA to clean, and to demagnetize an old Sony HE-2 tape head demagnetizer. Works great and can be found on ebay for $20 or less.
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Isn't Stainless Steel non magnetic ??
It depends on the type of stainless steel. They vary from pretty much totally non-magnetic to somewhat magnetic.
Also depends on the crystaline formation in the steel. Given the popularity of stainless vacuum mugs now, take a strong magnet and poke at different bits of it. Most of the body might be non-magnetic, but the bits where it curves and bends will be more magnetic due to being swaged into shape. The magnetic bits are also more prone to corrosion than the rest, but hopefully your mug isn't in conditions that are that corrosive :o
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I bought some of those cheap ceramic tweezers and was pleasantly surprised by them, but indeed they do have some issues.
Out of the box the fitting of the jaws differs greatly. some are near perfect others do not.
So If I grab a new one I first start by adjusting it.
I first bend it open more, to get a bit of extra "stiffness" in them for my big paws.
And also bend them in such a way that the extreme tip closes first.
Then I align them by fist loosening the adjustment screws, make sure they're tight afterwards.
As a last step I grind the ceramic to an exact fit and symmetry with a diamond disk in a dremel.
Some time ago I broke one of the jaws of a ceramic tweezers with my own stupidity.
I taped the metal of the tweezers shut to get a more solid handle and ground a chisel point on the tweezers.
This is a very handy tool for scraping small areas clean, even cutting 0.2mm enameled wire by chiseling it to the FR4.
when ground at around 60 degrees the ceramic chisel can take quite a lot of abuse and stays sharp a long time.
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To be honest with you, all I have is metal tweezers, and I have never tested them to see if they were magnetized.
Small parts seem to always stick to my tweezers. Ive always thought that the reason ultra small parts stuck to my tweezers was simply surface tension. But I suppose magnetism and parts with some steel in them could be at fault. I am going to have to check that out right now. If indeed I could replace and re-solder those small parts simply by using a ceramic tweezers (or demagnetizing my metal tweezers) that would be just great.
That has to be the most frustrating thing because time and heat kills (complicated or multilayer) boards.
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I always wipe my tweezers with a specialized flux cleaner, nothing sticks to them after that. Works even better than IPA.
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Clean with a dip in alcohol or acetone.
I demagnetize mine regularly by turning on a Weller-type soldering gun and passing the tweezers slowly through the loop of the copper heating element. You can pass one half of the tweezers through at a time, flip and do the other side.
Just be sure to have the tweezers well away from the gun before releasing the trigger on the gun.
Jon
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I clean the with whatever is appropriate for what I'm trying to get rid of, and demagnetize using a demagnetizer I made out of an electric hair trimmer that had the blades go dull, inside it was just an electromagnet and some levers, get rid of the moving parts and you have one of those cheap chinese demagnetizers.
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If you have a soldering gun, make a coil out of thick copper wire (like in the attached pic, solid copper wire for electrical power outlets in the house).
[attachimg=1]
Insert the tweezers in the middle of the coil, press the on switch to energize the coil, and keep the power on while slowly (5-10 seconds) removing the tweezers far away outside the coil.
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I got myself one of these titanium tweezers (https://www.ebay.com/itm/Titanium-0-15mm-edge-precision-fingerprint-tweezers-Apple-main-board-Repair-tool/133044766637?_trkparms=ispr%3D1&hash=item1efa1607ad:m:mTAJ0ahq9PcF1jmpxqZwxww&enc=AQAEAAACcIQvEcHUrT7nmUC3yY5qbPyaBN1nJEDYW8MyypsJPgXKMrJ5ZnoiL5k7zr%2FQKfBqzQtW7HrP5V1oQ0vQSQ%2BYTeabnScYfdyOv3wTxCi7BHuJCl0lYjr5%2FtDxEvg6GVrMvaHpnfQry265Anp7N8Rfol4DFsFNa44b8rF6%2Fu27%2FxZTnP4K3AgcA5c8zPRfjgeRDbVT6EyNPE%2BWOX82mbb7gO9%2BBS69XckbEdQ%2BD%2BBqEgbemZTzIPC%2F7RgyPp8NZqQ4SMplXTmPz47x9NnsV1Wop7IIVVBtkOvCH0qYfgr504amTEmvKvT6UABvy%2BXikHJyoj5sIVpLd6hj1KEAG9xOhzVDISJtdD3gHZAMDzvUKEuvtpCDqpXCjVFZMSvix6hfDpZsdZHmJHrL7NNmjIMwfOUC60wzrx%2BTF0VvV%2BTDl4jnm5FN6wyp18DsJ6qB006isM9UczYVCl%2F9rRqhQE6ckj%2Fr1k2pzTxyVnY7ZRbrE%2BDjaTmIhJ1sz17pErp1mYxO97qn8h2gEJRnSZ%2B%2FpAA26S4tWt01r4ET889%2F86KgvY3%2BAXFTLiCwHK1T7bhPaKsNrm2hdOsnJdcriZz3p%2BtGaddr85V5tYX3qxF2KlkvZNETCN8yJRMoCjHoHeSNaxikkqxPgDCdofsqObQtU8u74l5EyXi2az8oCJLD%2FNBe5BauyFc6stJbScwCcIat4hVzXo3R7IU0xh%2FfjHxBlsTFQFFN2mo4aXQ6JT8ZGlY%2FOOC%2F0gOJ9243zkCFhw8Sh43hGRfwuCt2zS%2FDI%2F%2F1RRGR4rh6Wl2Tzx%2Bx18NInSSooe6UnphWNJJc09duonAsLuQZRw%3D%3D&checksum=133044766637dc2673f3b2da4ca8aef8624ee7efe660).
They don't need demagnetization, but for screwdrivers, I use something like this:
(https://i.ebayimg.com/images/g/eaMAAOSwZ8ZXB2ox/s-l300.jpg)
Works just fine, and doubles as magnetizer if needed.
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Crude vintage head demagnetiser, works well on tweezers!
[attachimg=1]
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Hi,
I can confirm that watchmaker's demagnetizers are simply a coil with a push button.
Also, there are watchmaker tweezers made from brass that are non magnetic.
Regards.
Yes, this device is basically just a coil with a push button (in the line cord). It works very well and only cost a few dollars (vintage gear).
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I love freshly cleaned tweezers. But I learn to get by in betwixt cleanings. Flux residue on the tweezers can be useful, or at least more manageable, when you learn to heat the tweezers with your iron.
When doing SMD assembly, it usually helps to use a pickup tool, anyway. Once the parts are flat on the board, it is usually no problem to manipulate them even when your tweezers are sticky with flux. The flux is annoying when you pick up a part wrong, to begin with. In this case, touching the tweezers with your iron can help the part to let go. By placing the tweezers at the right height and orientation, you can try to aim for the part to land rightside up when it releases.
Also, when your tweezers get stuck together in the closed position, a quick touch with a hot iron is often all it takes to get them to open.
When a decoupling cap goes missing from the board, I heat the tweezers briefly (under the microscope) and then quickly poke and snatch the tweezers into a pile of ceramic caps, and usually 1 (or sometimes more than 1) come out with the tweezers, due to the flux residue on there. When I'm soldering SMD PCB, everything is based around the microscope.
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I clean them with acetone or a similar suitable solvent for whatever they are contaminated with.
To demagnetize any tools that I don't want magnetic I use my degaussing wand that I got back when I was working on a lot of CRT monitors and TVs.